Biodegradable polycarbonate-b-polypeptide and polyester-b-polypeptide block copolymers:: Synthesis and nanoparticle formation towards biomaterials

The amino poly(trimethylene carbonate)-NHt-Boc (PTMC-NHt-Boc) and poly(E-caprolactone)-NHt-Boc (PCL-NHt-Boc) were synthesized by ring-opening polymerization (ROP) of TMC or CL and subsequently deprotected into the corresponding PTMC-NH2 and PCL-NH2. These functional homopolymers were used as macroinitiators for the ROP of gamma-benzyl-L-glutamate N-carboxyanhydride (BLG), consequently, giving the respective diblock copolymers PTMC-b-PBLG and PCL-b-PBLG in almost quantitative yields. The (co)polymers have been characterized by NMR and SEC analyses. DSC and IR studies confirmed the block structure of the copolymers and highlighted a phase separation between the rigid peptide (alpha-helix conformation) and the more flexible polyester segments. The self-assembly and the degradation behaviors of the copolymers depended on the nature of the polyester block and on the copolymer composition. Nanoparticles obtained from PBLG block copolymers were twice smaller (R-H < 100 nm) than those formed from PTMC and PCL homopolymers. Finally, their enzymatic degradation revealed that PTMC nanoparticles degraded faster than those made of PCL.